London - Brazilian driver Felipe Massa is to retire definitively from Formula One at the end of the season he announced on Saturday.
The 36-year-old Williams pilot -- who won 11 Grand Prix to date -- decided to call it a day as his team are yet to confirm their line-up for next season.
Massa had indicated he would like to compete again next year -- having originally changed his mind about retiring at the end of 2016 -- but Williams are thought to be favouring giving Poland's Robert Kubica, who has performed miracles to return after a terrible crash in a rally in 2011, the drive alongside Canadian Lance Stroll.
"I agreed to return this season to help Williams when the call came," said Massa.
"I have now enjoyed four great years with the team, but my career in Formula 1 will finally come to an end this season."
Massa, who suffered a serious injury when hit by the suspension of a rival's car in the Hungarian Grand Prix in 2009, said he cherished his time in the sport since making his debut in 2009.
"I take so many great memories with me as I prepare for my final two races in Brazil and Abu Dhabi, and although they will be emotional, I am looking forward to ending on a high note and preparing for a new chapter in my career," said Massa.
His best finish overall was runner-up for Ferrari to Lewis Hamilton in 2008 after a thrilling season long battle.
Williams deputy team principal Claire Williams said Massa had been an absolute dream to work with.
"I would like to thank Felipe for all he has done for the team over the last four years. It has been an absolute pleasure to work with him," she said in a statement.
"We are especially grateful that he agreed to postpone his retirement from F1 for a year, after Valtteri (Bottas) joined Mercedes, which demonstrated the depth of the relationship we built during our time together.
"We appreciate that it wasn't an easy decision for him to return, after having such an emotional send-off at the end of last year.
"On behalf of (owner and team principal) Sir Frank (Williams, her father), and all the team, we give our very best wishes to Felipe for the future."